The need for effective therapeutic treatment of patients has resulted in the development of a variety of pharmaceutical formulation delivery techniques. One traditional technique involves the oral delivery of a pharmaceutical formulation in the form of a pill, capsule, elixir, or the like. However, oral delivery can in some cases be undesirable. For example, many pharmaceutical formulations may be degraded in the digestive tract before they can be effectively absorbed by the body. Inhaleable drug delivery, where an aerosolized pharmaceutical formulation is orally or nasally inhaled by a patient to deliver the formulation to the patient's respiratory tract, has proven to be a particularly effective and/or desirable alternative. In one inhalation technique, an aerosolized pharmaceutical formulation provides local therapeutic treatment and/or prophylaxis to a portion of the respiratory tract, such as the lungs, to treat respiratory diseases such as asthma and emphysema and/or to treat local lung infections, such as fungal infections and cystic fibrosis. In another inhalation technique, a pharmaceutical formulation is delivered deep within a patient's lungs where it may be absorbed into the blood stream for systemic delivery of the pharmaceutical throughout the body. Many types of aerosolization devices exist including devices comprising a pharmaceutical formulation stored in or with a propellant, devices that aerosolize a dry powder, devices which use a compressed gas or other mechanism to aerosolize a liquid pharmaceutical formulation, and similar devices.
One conventional type of aerosolization device is commonly referred to as a nebulizer. A nebulizer comprises a container having a reservoir which contains a liquid pharmaceutical formulation. The liquid pharmaceutical formulation generally comprises an active agent that is either in solution or suspended within a liquid medium. Energy is introduced into the reservoir to aerosolize the liquid pharmaceutical formulation so that it may be delivered to the lungs of a user. In one type of nebulizer, generally referred to as a jet nebulizer, compressed gas is forced through an orifice in the container. The compressed air forces liquid to be withdrawn through a nozzle, and the withdrawn liquid mixes with the flowing gas to form aerosol droplets. A cloud of the droplets is then administered to the user's respiratory tract. In another type of nebulizer, generally referred to as a vibrating mesh nebulizer, energy such as ultrasonic waves are generated to vibrate a mesh. This vibration of the mesh aerosolizes the liquid pharmaceutical formulation to create an aerosol cloud that is administered to the user's lungs. Nebulizers are sometimes cumbersome to use. However, nebulizers are particularly useful in delivering an aerosolized pharmaceutical formulation to a hospitalized or non-ambulatory patient; in delivering large doses of aerosolized active agent; and/or when delivering an aerosolized pharmaceutical formulation to a child or other patient unable to receive a dry powder or propellant based pharmaceutical formulation.
Nebulizers are particularly useful for delivering an aerosolized pharmaceutical formulation to the respiratory tract of a patient who is breathing under the assistance of a ventilator. However, there are problems associated with the introduction of the aerosolized pharmaceutical formulation into the ventilator circuit. For example, by introducing the aerosolized pharmaceutical formulation into the inspiratory line of the ventilator, significant residence volume exists between the point of introduction and the patient's lungs. Accordingly, large volumes of aerosolized pharmaceutical formulation are needed and much of the volume is lost to the exhalation line. This problem is exacerbated when the nebulizer is used in conjunction with ventilators having continual bias flows. In addition, the large residence volume in the ventilator line may dilute the aerosolized pharmaceutical formulation to an extent where the amount delivered to the patient is difficult to reproduce consistently.
Therefore, it is desirable to provide a way to introduce an aerosolized pharmaceutical formulation to a ventilated patient in an effective and consistent manner. It is further desirable to introduce the aerosolized pharmaceutical formulation in a manner that reduces the loss of active agent. It is further desirable to introduce the aerosolized pharmaceutical formulation in a manner that is applicable over a broad range of ventilators and a broad range of practices.